For closed captions (CC) , we've found that if the learner/user does not learner click the CC button that we've coded (to display cc) before moving to the page/slide, the CCs for not only the base layer, but also for the pop-up layers will display all at the same time (or more than one will display, overlapping the base cc).
(We saw a slightly similar post here, but more complex involving video, but that post did not present a solution.)
Via testing, it's seems that the CC will perform correctly as coded if the user/learner has already turned the CC "on" before entering the page/slide.
Is this possibly a bug or requirement for pop-up layers to function normally? (That the user must have CC "on" before moving to the page/slide)